From the Super Mario Wiki
Splash Circuit is a race track in Mario Kart Arcade GP DX. This track appears as the 1st and 3rd rounds of the Mario Cup, while Tropical Coast appears as the 2nd and 4th rounds of the same cup. The layout of this track is generally the same and based off Mario Highway from Mario Kart Arcade GP and Mario Kart Arcade GP 2; but the theme of the track is significantly different from the two games.
The course begins at one of the straightest points of the track with the racers going straight, but the section that leads to the underwater section is blocked. Instead, the racers take curves at one of the tightest turns of the track to the east side of the race course. Along the way, there are Dash Panels that can help the kart reach it's maximum speed. After the final Dash Panel, the karts make a slight left turn in which the track joins the Tropical Coast path that is just after the underwater section. After the karts pass the Mario Kart tunnel, the karts turn sharply to the right, which leads to the finish line. The racers do 4 laps in this track to finish a race, except in 150cc and Mirror, where the racers do 5 laps.
Various signs appear in this course. Some signs are based off the playable characters, and there are also signs based off Princess Daisy. The words for the Start/Finish sign is Mario Circuit. The Airship appears in front of the Diving sign and above the blocked underwater section.